Bug#715019: linux-image-3.10-rc7-amd64: Bcache (with cache on LVM?) stops system from shutting down

Ben Hutchings ben at decadent.org.uk
Fri Jul 5 18:42:22 UTC 2013

On Fri, Jul 05, 2013 at 04:56:58PM +0300, Jarno Elonen wrote:
> Package: src:linux
> Version: 3.10~rc7-1~exp1
> Severity: normal
> My bcache test setup is working otherwise well, but when enabled,
> the "poweroff" or "reboot" commands never finish.
> Block device stack is as follows:
>    - DRBD on LVM on BCACHE on MD0 (raid10) on HDD (sata)
>    - with: bcache cache device on LVM on SSD
> The shutdown sequence gets to the very last line ("booting now" or
> something to that effect), but instead of booting, it pauses for a long
> time and then starts writing out ATA errors and IO error reports from
> bcache, saying bcache failed to read the cache device.

Please provide the error messages.  A screenshot will do, though a
text log (using netconsole or serial console) would be preferable.

> I guess that is to
> be expected as LVM, which contains contains the cache, has apparently
> been shut down at that point.
> This appears to be a bug in either the (ordering of) shutdown procedures
> or bcache. I've tried manually stopping bcache and removing the module
> before booting, and that indeed makes the shutdown work as expected.

So this might be considered a bug in the lvm2 package.  (Actually,
I've never understood why lvm2 removes logical volumes during
shutdown/reboot at all.)  However, lvm2 never removes the root logical
volume because it's detected as busy (still mounted).  Usage by bcache
should - but apparently does not - result in that same busy status,
which would presumably be a kernel bug.


Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus

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